In slashing the price of the Lumia 900 to $49.99 this weekend, Nokia's gorgeous, super-intuitive Windows Phone is now -- as the poets at Gizmodo put it -- "crazy cheap." Other smartphones that cost $50 or less feel plasticky and inexpensive, have lousy screens and use outdated technology. Not so with the Lumia 900, which is premium all-around and flies in everyday use.

And yet: As good as the Lumia 900 is, and as enticing as it may be at $49.99, most cell phone shoppers should still steer clear. As Reuters points out, the recent announcement that the Lumia 900 will not be fully upgraded to the upcoming Windows Phone 8 operating system -- and this is the generally non-editorializing Reuters talking here -- "render[s] them obsolete."

When Windows Phone 8 -- the next-generation operating system for Microsoft's Windows Phone devices, which is the mobile OS that the Lumia 900 runs -- arrives this fall, the Lumia 900 will not be eligible to download it. Like many other current Windows Phones, the Lumia will instead be upgraded to Windows Phone 7.8, which will include some, but not at all, of the features in Windows Phone 8.

As the numerical difference between 7.8 and 8 implies, Windows Phone 7.8 comes up just short of Windows Phone 8. The main concern for potential Lumia 900 buyers would seem to be about apps: Windows Phone 7.8 will not be able to run most of the apps developed for Windows Phone 8, which means that Lumia 900 customers could be stuck with a smaller app library than their friends who wait for a Nokia phone that can run Windows Phone 8.

While Windows Phone 7.8 will certainly receive the jazzy new start screen of WP8 and a few other features, it is hard to recommend the Lumia 900 when Windows Phone 8 -- and the faster, more fully capable smartphones running it -- are so imminent. Indeed, I called it a "great smartphone you shouldn't buy" in a recent column, largely because of the unfortunate half-upgrade that's being offered. If you're planning on keeping the Lumia 900, you have to be thinking: "What other upcoming updates will my phone not be fully eligible for?"

Now, it could be that you are in the market for a smartphone that is easy to use, and with a large, attractive screen that can make phone calls and send text messages and access your email and do all of the basics. You don't care about apps, and you don't even know how to upgrade your operating system: You just want a high-quality smartphone that can do the basics. For you, the $49 Lumia 900 is a great deal, and you should jump on it, if you need a smartphone now and want to save some money.

For most everyone else, patience is a virtue. Wait for the next Lumia smartphone, running Windows Phone 8, to arrive some time in the autumn if you can. You will be rewarded with a faster smartphone that will be capable of more than the Lumia 900; though you might spend a little more cash, the price difference will include all of the apps and new features coming with Windows Phone 8, not just the select ones that are being tacked on to Windows Phone 7.8.

The announcement of Windows Phone 8 -- and, too, Windows Phone 7.8 -- means a difficult period for Nokia, whose flagship smartphone is suddenly outdated and who cannot release a smartphone that won't be outdated for another several months. That's a pretty good argument for making new hardware available immediately after you announce it, rather than waiting a few months and having to rely on obsolete products and flashy price cuts to entice buyers who know that the Next Big Thing is coming soon.

For those consumers who need a smartphone now and don't care about apps or bells and whistles, and just want a well-made, fully-functional smartphone that can do the basics, a $50 Lumia 900 is a steal. For everyone else -- and that's most of you -- it's probably better to wait for 8 (Windows Phone 8, that is).